There can always be an mathematical explaination sure. But that won't help you as a designer if there is no way to know/apply that explaination beforehand. There is probably also a (quite complex) mathematical rule to drive your car on a public road, so it should be simple to implement automatic driving, right?
Optical weight is nice and all (and a better simple rule than just spacing things by equal distance), but in the end you also have other phenomena (humans perceive horizontal lines different than vertical ones etc.)
Just the seemingly simple task of spacing out letters can get complicated pretty fast if it should look pleasing as in "as if there was no design there".
It's also the case that some of the simplest and most intuitive possible mathematical rules are going to look less good than some less mathematically elegant ratio, like picking line spacing for body text which is exactly the font-size or exactly twice the font-size rather than somewhere between 1.2x - 1.5x
Optical weight is nice and all (and a better simple rule than just spacing things by equal distance), but in the end you also have other phenomena (humans perceive horizontal lines different than vertical ones etc.)
Just the seemingly simple task of spacing out letters can get complicated pretty fast if it should look pleasing as in "as if there was no design there".